Solvent Separation System and Method

ABSTRACT

The disclosure provides a solvent separation system and a solvent separation method using the solvent separation system.

TECHNICAL FIELD

The present invention relates to a system and method for separating asolvent from a solution.

BACKGROUND ART

The separation and recovery of solvents from solutions is widely carriedout throughout various industries. The solvents to be separated containsolutes selected from inorganic compounds and organic compounds.Consequently, the recovered solvents frequently require a purificationstep. Purified solvents are then sold as solvents for use in processapplications of the chemical industry or in various other applications.

Among these solvents, water is a typical solvent that contains varioussolutes in many cases and generally cannot be used directly as water.Thus, purification and regeneration are required to obtain usable waterfrom this low-quality water.

Examples of water purification include desalination of seawater andpurification of industrial wastewater. In the prior art, purification ofwater is carried out by energy-intensive methods requiring comparativelyhigh temperature and pressure such as distillation or reverse osmosis.Thus, attention is being increasingly focused on forward osmosistechnology (Patent Document 1).

Consequently, there is a desire for a process that enables purificationand regeneration of water to be carried out efficiently.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: U.S. Patent Application Publication No. 2011/0272355

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

An object of the present invention is to provide a system and method forefficiently separating a solvent from a solution.

Means for Solving the Problems

The inventors of the present invention conducted extensive studies tosolve the aforementioned problems. As a result, it was found that, in asolvent purification system using a forward osmosis process, when asolvent is absorbed from an osmotic agent stream into which a solventhas migrated into a thermal phase change polymer stream, by controllingthe respective temperatures of the liquid streams involved in thisabsorption so as to mutually have a specific relationship, solventseparation can be carried out more efficiently, thereby leading tocompletion of the present invention.

Namely, the present invention is as indicated below.

[1] A solvent separation system, comprising:

a first step for causing a feed stream a containing a solute and asolvent b to flow counter or parallel to an osmotic agent stream dthrough a semipermeable membrane o and causing the solvent b containedin the feed stream a to pass through the semipermeable membrane o andmigrate into the osmotic agent stream d to obtain a flow e,

a second step for mixing the flow e containing the solvent b and theosmotic agent stream d with a thermal phase change polymer stream k toobtain a flow f, followed by separating the flow f containing thesolvent b, the osmotic agent stream d and the thermal phase changepolymer stream k into the osmotic agent stream d and a flow h containingthe solvent b and the thermal phase change polymer stream k, and

a third step for heating the flow h followed by separating into thesolvent b and the thermal phase change polymer stream k; wherein,

the second step simultaneously satisfies the following conditions (1)and (2):

(1) the relationship between a temperature Tk of the thermal phasechange polymer stream k prior to mixing and a temperature Tf of the flowf after mixing is such that Tk−Tf=0.1° C. to 80° C., and

(2) the temperature Tf of the flow f after mixing is equal to or higherthan the cloud point of the flow f.

[2] The system described in [1], wherein the relationship between atemperature Te of the flow e prior to mixing and the temperature Tf ofthe flow f after mixing is such that Te−Tf=0.1° C. to 80° C.

[3] The system described in [1] or [2], wherein the solvent b is water.

[4] The system described in any of [1] to [3], wherein the thermal phasechange polymer contained in the thermal phase change polymer stream k isa copolymer of ethylene oxide and propylene oxide, and the ends thereofare either hydroxyl groups or one or more of the end hydroxyl groups issubstituted with one or more types of groups selected from the groupconsisting of an alkyl group, phenyl group, allyl group and aryl group.

[5] The system described in any of [1] to [4], wherein the flow hcontaining the solvent b and the thermal phase change polymer stream khas a cloud point between 50° C. to 200° C.

[6] The system described in any of [1] to [5], wherein the osmotic agentcontained in the osmotic agent stream d is one or more types selectedfrom the group consisting of an inorganic base, organic base, salt,ionic polymer, ionic liquid, nonionic polymer and organic compound.

[7] The system described in any of [1] to [6], wherein the first step iscarried out by a forward osmosis process.

[8] A solvent separation method, comprising: separating a solvent b froma feed stream a containing the solvent b and a solute selected from aninorganic compound and an organic compound using the system described inany of [1] to [7].

[9] A solvent separation system, comprising:

a first step for causing a feed stream a containing a solute and asolvent b to flow counter or parallel to an osmotic agent stream dthrough a semipermeable membrane o and causing the solvent b containedin the feed stream a to pass through the semipermeable membrane o andmigrate into the osmotic agent stream d to obtain a flow e,

a second step for introducing the flow e, containing the solvent b andthe osmotic agent stream d, and a thermal phase change polymer stream kinto a counter flow extraction device S to cause the solvent b tomigrate from the flow e into the thermal phase change polymer stream kfollowed by separating into the osmotic agent stream d and a flow hcontaining the solvent b and the thermal phase change polymer stream k,and

a third step for heating the flow h followed by separating into thesolvent b and the thermal phase change polymer stream k.

[10] The system described in [9], wherein the relationship between atemperature Tk of the thermal phase change polymer stream k prior tomixing and a temperature Ts within the counter flow extraction device Sin the second step is such that Tk−Ts=0.1° C. to 80° C.

[11] The system described in [9] or [10], wherein the relationshipbetween a temperature Te of the flow e prior to mixing and thetemperature Ts within the counter flow extraction device S in the secondstep is such that Te−Ts=0.1° C. to 80° C.

[12] The system described in any of [9] to [11], wherein the solvent bis water.

[13] The system described in any of [9] to [12], wherein the thermalphase change polymer contained in the thermal phase change polymerstream k is a copolymer of ethylene oxide and propylene oxide, and theends thereof are either hydroxyl groups or one or more of the endhydroxyl groups is substituted with one or more types of groups selectedfrom the group consisting of an alkyl group, phenyl group, allyl groupand aryl group.

[14] The system described in any of [9] to [13], wherein the flow hcontaining the solvent b and the thermal phase change polymer stream khas a cloud point between 50° C. to 200° C.

[15] The system described in any of [9] to [14], wherein the osmoticagent contained in the osmotic agent stream d is one or more typesselected from the group consisting of an inorganic base, organic base,salt, ionic polymer, ionic liquid, nonionic polymer and organiccompound.

[16] The system described in any of [9] to [15], wherein the first stepis carried out by a forward osmosis process.

[17] A solvent separation method, comprising: separating a solvent bfrom a feed stream a containing the solvent b and a solute selected froman inorganic compound and an organic compound using the system describedin any of [9] to [16].

[18] A solvent separation device, provided with:

a unit A that has a structure in which a feed stream a and an osmoticagent stream d flow through a semipermeable membrane o in the form ofcounter flow or parallel flow, and has an inlet port for the feed streama, a discharge port for a flow c obtained after the feed stream a hasflown counter or parallel to the osmotic agent stream d through thesemipermeable membrane o, an inlet port for the osmotic agent stream d,and a discharge port for a flow e obtained after the osmotic agentstream d has flown counter or parallel to the feed stream a through thesemipermeable membrane o,

a counter flow extraction device S that has a structure in which theflow e is caused to flow counter to the thermal phase change polymerstream k and the solvent b in the flow e is extracted into the thermalphase change polymer stream k to obtain a flow h, and has an inlet portfor the flow e and a discharge port for the flow e following extraction,an inlet port for the thermal phase change polymer stream k, a dischargeport for the flow h, and a temperature control function, and

a unit B that has a heat exchanger q2 for heating the flow h and aseparator B, wherein the separator B has a function that separates theflow h into the thermal phase change polymer stream k and the solvent b,and the separator B has an inlet port for the flow h, a discharge portfor the thermal phase change polymer stream k, and a discharge port forthe solvent b.

Effects of the Invention

According to the present invention, a solvent can be efficientlyseparated from a solution.

The present invention can be preferably applied to applications such asdesalination of seawater, purification of industrial wastewater,concentration of valuable resources, purification of injection waterused during excavation of gas fields and oil fields for shell gas andoil, or treatment of produced water discharged accompanying excavationof gas fields and oil fields for shell gas and oil.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram for explaining an overview of anembodiment of the system of the present invention.

FIG. 2 is a conceptual diagram for explaining an overview of anotherembodiment of the system of the present invention.

FIG. 3 is a conceptual diagram for explaining an example of a counterflow extraction device.

FIG. 4 shows an example of an embodiment of the system of the presentinvention.

FIG. 5 shows another example of an embodiment of the system of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The following provides a specific explanation of details of the presentinvention.

An explanation is first provided of the relationships and functions ofeach element in the present invention.

A solute refers to a substance selected from inorganic compounds andorganic compounds and preferably dissolves in a solvent b.

A feed stream a is a solution composed of the solvent b and a solute.The solvent b is a liquid. Examples of this feed stream a includeseawater (in which, for example, sodium chloride is the solute and wateris the solvent), industrial wastewater (in which, for example, varioustypes of inorganic substances or organic substances are the solute andwater is the solvent), liquids containing valuable resources (in which,for example, valuable resources such as a pharmaceutical or latex is thesolute and water is the solvent), and produced water discharged from gasfields or oil fields (in which, for example, sodium chloride, oil or gasis the solute and water is the solvent). Examples of produced waterinclude water containing salt that returns to the surface together withgas and oil produced after having subjected shale to hydraulicfracturing with a fracturing fluid. This produced water contains a highconcentration of salt consisting mainly of sodium chloride.

The solvent b can be any inorganic solvent or organic solvent. Thesolvent b is present as a liquid in the feed stream a. There are manycases in which this solvent b is water.

An osmotic agent stream d is a liquid that has a higher osmotic pressurethan the feed stream a and does not cause significant degeneration of asemipermeable membrane o. When contact is made between the feed stream aand the osmotic agent stream d through the semipermeable membrane o, thesolvent b in the feed stream a migrates into the osmotic agent stream dby permeating the semipermeable membrane o. As a result of using theosmotic agent stream d in this manner, a forward osmosis process can beactivated using the semipermeable membrane o.

A forward osmosis process refers to a process that causes two liquidshaving different osmotic pressures to make contact through thesemipermeable membrane o, causing a solvent to migrate from the lowosmotic pressure side to the high osmotic pressure side.

The aforementioned osmotic agent stream d is composed of an osmoticagent and a solvent thereof as necessary.

The osmotic agent can be, for example, an inorganic base, organic base,salt, ionic polymer, ionic liquid, nonionic polymer or organic compound.

The aforementioned inorganic base is, for example, sodium hydroxide,potassium hydroxide, calcium hydroxide or barium hydroxide.

The aforementioned organic base is, for example, tetraethylammoniumhydroxide.

The aforementioned salt is, for example, sodium chloride, potassiumchloride, ammonium chloride, sodium carbonate, sodium silicate, sodiumsulfate, sodium sulfite, sodium phosphate, sodium formate, sodiumsuccinate, sodium tartrate, sodium thiosulfate, lithium sulfate,ammonium sulfate, ammonium carbonate, ammonium carbamate, zinc sulfate,copper sulfate, iron sulfate, magnesium sulfate, aluminum sulfate,disodium hydrogen phosphate, monosodium dihydrogen phosphate, potassiumphosphate, potassium carbonate, manganese sulfate or sodium citrate.

These inorganic bases, organic bases or salts are dissolved in a solventin order to be used for the osmotic agent stream d. Water, for example,is preferably used for the solvent in this case.

The aforementioned ionic polymer is, for example, polyacrylic acid, lowmolecular weight sodium polyethylene sulfonate, sodium polymethylacrylate or a copolymer thereof. These ionic polymers are dissolved in asolvent in order to be used for the osmotic agent stream d. Water, forexample, is preferably used for the solvent in this case.

The aforementioned ionic liquid is a salt having a melting point of 100°C. or higher. More specifically, examples thereof include imidazoliumsalts, pyrrolidinium salts, piperidinium salts, pyridinium salts,morpholinium salts, ammonium salts, phosphonium salts and sulfoniumsalts. These ionic liquids are listed in, for example, the ionic fluidcatalog published by Sigma-Aldrich (October 2012), and can be acquiredas commercially available products. Specific examples thereof includebutyltrimethylammonium bis(trifluoromethylsulfonyl)imide,1-butyl-3-methylimidazoilum hexafluorophosphate, tetrabutylphosphoniummethanesulfonate, 1-butyl-3-methylpyridiniumbis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylpyrrolidniumbis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylpiperidiniumbis(trifluoromethylsulfonyl)imide, triethylsulfoniumbis(trifluoromethylsulfonyl)imide, tetrabutylphosphoniummethanesulfonate and 4-ethyl-4-methylmorpholinium methyl carbonate.These ionic liquids can be used directly for the osmotic agent stream dor can be used after dissolving in a solvent (such as water).

The aforementioned nonionic polymer is, for example, dextran,polyethylene glycol, polyethylene oxide, polypropylene glycol,polypropylene oxide, or a copolymer of ethylene oxide and propyleneoxide. The aforementioned polyethylene glycol, polypropylene glycol andcopolymer of ethylene oxide and propylene oxide may have all or aportion of the hydrogen atoms thereof substituted with an alkyl group,phenyl group, allyl group or aryl group. These nonionic polymers aredissolved in a solvent in order to be used for the osmotic agent streamd. Water, for example, is preferably used for the solvent in this case.

Preferable examples of the aforementioned organic compounds includeglycerol, ethylene glycol, diethylene glycol, triethanolamine, ethanol,propanol, acetone, diethyl ether, monoethers of ethylene glycol,monoethers of diethylene glycol, diethers of ethylene glycol, diethersof diethylene glycol, monoesters of ethylene glycol, monoesters ofdiethylene glycol, diesters of ethylene glycol, diesters of diethyleneglycol and polysaccharides (such as sugar dimers or trimers). Examplesof the aforementioned sugars include glucose and fructose. These organiccompounds are dissolved in a solvent in order to be used for the osmoticagent stream d. Water, for example, is preferably used for the solventin this case.

The osmotic agent in the present embodiment is preferably one or moretypes selected from the group consisting of ammonium sulfate, disodiumhydrogen phosphate, sodium thiosulfate, sodium sulfite and magnesiumsulfate. Ammonium sulfate and sodium thiosulfate are particularlypreferable since they demonstrate high osmotic pressure when dissolvedin water enabling a larger amount of solvent to migrate through thesemipermeable membrane o. Sodium thiosulfate is particularly preferabledue to the low reverse salt flux thereof.

These osmotic agents can be used alone or can be used after mixing. Theosmotic agent stream d may also contain a trace amount of the polymercomponent contained in the thermal phase change polymer flow k to besubsequently described.

The solvent in the osmotic agent stream d is preferably the same type ofsolvent as the solvent b to be separated from the feed stream a. In thecase the solvent b is water, the solvent in the osmotic agent stream dis preferably also water.

The concentration of the osmotic agent in the osmotic agent stream d isset so as to be higher than the osmotic pressure of the feed stream a.The osmotic pressure of the osmotic agent stream d may fluctuateprovided it fluctuates within a range that is higher than the osmoticpressure of the feed stream a. Either of the following methods can beused to determine an osmotic pressure difference between two liquids.

(1) Case of biphasic separation after mixing the two liquids: The liquidthat increases in volume following biphasic separation is determined tohave higher osmotic pressure.

(2) Case of absence of biphasic separation after mixing the two liquids:The two liquids are allowed to contact through the semipermeablemembrane o, and the liquid that has increased in volume after thepassage of a certain amount of time is determined to have higher osmoticpressure. Although the certain amount of time at this time is dependenton the difference in osmotic pressure, it is generally from severalminutes to several hours.

The semipermeable membrane o is a membrane having a function that allowsthe solvent b but not the solute to pass through. The blocking rate ofthe semipermeable membrane o with respect to sodium chloride ispreferably 10% or more, more preferably 50% or more and even morepreferably 98% or more. Examples of the form of the semipermeablemembrane o include a hollow fiber, flat sheet membrane and spiralmembrane.

Examples of the material that composes the semipermeable membrane oinclude materials used as reverse osmosis membranes in the prior art.Specific examples thereof include materials having a polyamide layerprovided on the surface of a supporting membrane composed of celluloseacetate or polysulfone.

The flow e is a flow composed of the osmotic agent stream d and thesolvent b that has passed through the semi-permeable membrane o from thefeed stream a. In other words, the flow e is formed as a result of thesolvent b migrating from the feed stream a into the osmotic agent streamd through the semipermeable membrane o.

A thermal phase change polymer refers to a polymer having propertiesthat make the polymer compatible with the solvent b at a temperatureequal to or lower than the cloud point, and properties that cause apolymer-rich phase and a solvent b-rich phase to undergo phaseseparation at a temperature above the cloud point. The thermal phasechange polymer has a function that generates high osmotic pressure inthe thermal phase change polymer stream k, and is the driving forcebehind the migration of the solvent b from the flow e to the thermalphase change polymer stream k.

Specific examples of this thermal phase change polymer include ethoxyhydroxyethyl cellulose, polyvinyl alcohol, poly-n-vinylcaprolactam,polyethylene glycol, polypropylene oxide, copolymers of ethylene oxideand propylene oxide, polyalkylene oxide, Triton® X-114, polyvinylalcohol acetate, cellulose ethoxylate, acrylate-acrylic acid copolymer,phosphorous-containing polyolefins, cellulose ethers partiallysubstituted with an ethyl group or methyl group, copolymers of vinylalcohol and methyl vinyl ketone, copolymers of propylene glycolmethacrylate and methyl methacrylate, (co)polymers of maleic aciddiesters; and the polymer described in U.S. Patent ApplicationPublication No. 2011/0272355.

The thermal phase change polymer is preferably a polymer thatdemonstrates high osmotic pressure in the thermal phase change polymerstream k and lowers the cloud point of the flow h. This thermal phasechange polymer is preferably selected from among:

(1) polymers obtained by substituting one or more end hydroxyl groups ofpolyethylene glycol with one or more types of groups selected from thegroup consisting of an alkyl group, phenyl group, allyl group and arylgroup, or

(2) polymers obtained by substituting one or more end hydroxyl groups ofa copolymer of ethylene oxide and propylene oxide with one or more typesof groups selected from the group consisting of an alkyl group, phenylgroup, allyl group and aryl group, and

is more preferably selected from among:

(1) a polymer obtained by substituting one or more end hydroxyl groupsof linear polyethylene glycol with an alkyl group, phenyl group, allylgroup or aryl group, or

(2) a polymer obtained by substituting one or more end hydroxyl groupsof a linear copolymer of ethylene oxide and propylene oxide with analkyl group, phenyl group, allyl group or aryl group.

It is advantageous for the thermal phase change polymer stream k to havelow viscosity in order to allow the solvent b to migrate from the flow einto the thermal phase change polymer stream k. Thus, it is preferablethat the thermal phase change polymer contained in the thermal phasechange polymer stream k have a low molecular weight from this viewpoint.On the other hand, it is advantageous for the molecular weight of thethermal phase change polymer contained in the flow h to be high in orderfor the solvent b to be obtained at high purity by the separator B to besubsequently described. When considering both of these requirements, theweight-average molecular weight of the thermal phase change polymerbased on polystyrene as measured by gel permeation chromatography ispreferably 300 to 10,000, more preferably 500 to 5,000 and even morepreferably 500 to 1,500.

The thermal phase change polymer may be used directly for the thermalphase change polymer stream k or may be used for the thermal phasechange polymer stream k in the form of a solution in which it isdissolved in a suitable solvent. In the case the thermal phase changepolymer stream k contains a solvent, the solvent is preferably the sametype of solvent as the solvent b to be separated from the feed stream a.

The concentration of the thermal phase change polymer in the thermalphase change polymer stream k can be suitably set according to the valueof a desired osmotic pressure. The osmotic pressure of the thermal phasechange polymer stream k is higher than the osmotic pressure of the flowd and may fluctuate provided it is within that range. The thermal phasechange polymer stream k may contain a trace amount of the aforementionedosmotic agent.

The flow f refers to a mixture of the flow e and the thermal phasechange polymer stream k. Thus, the flow f contains the solvent b, theosmotic agent stream d and the thermal phase change polymer stream k.Solvents thereof are contained in the flow f in the case the thermalphase change polymer stream k contains a solvent, the osmotic agentstream d contains a solvent or both streams thereof contain a solvent.

The flow h refers to a flow composed of the solvent b that has migratedfrom the flow e and the thermal phase change polymer stream k. This flowh may contain a trace amount of an osmotic agent. This flow h is in astate in which the solvent b and the thermal phase change polymer streamk are dissolved in a single phase.

The following provides an explanation of the solvent separation systemof the present invention with reference to the drawings as necessary.

The solvent separation system of the present invention is a solventseparation system comprising:

a first step for causing the feed stream a containing a solute and thesolvent b to flow counter or parallel to the osmotic agent stream dthrough the semipermeable membrane o and cause the solvent b containedin the feed stream a to pass through the semipermeable membrane o andmigrate into the osmotic agent stream d to obtain the flow e,

a second step for mixing the flow e containing the solvent b and theosmotic agent stream d with the thermal phase change polymer stream k ata mixing point α to obtain the flow f, followed by separating the flow fcontaining the solvent b, the osmotic agent stream d and the thermalphase change polymer stream k into the osmotic agent stream d and theflow h containing the solvent b and the thermal phase change polymerstream k, and

a third step for heating the flow h followed by separating into thesolvent b and the thermal phase change polymer stream k, wherein

the second step simultaneously satisfies the following conditions (1)and (2):

(1) the relationship between the temperature Tk of the thermal phasechange polymer stream k prior to mixing and the temperature Tf of theflow f after mixing is such that Tk−Tf=0.1° C. to 80° C., and

(2) the temperature Tf of the flow f after mixing is equal to or higherthan the cloud point of the flow f. In the above description, therelationship between the temperature Te of the flow e prior to mixingand the temperature Tf of the flow f after mixing is preferably suchthat Te−Tf=0.1° C. to 80° C.

The temperature Tk of the thermal phase change polymer stream k refersto the temperature of the thermal phase change polymer stream k at alocation near the mixing point α where the thermal phase change polymerstream k merges with the flow e.

The temperature Tf of the flow f refers to the temperature of the flow fformed as a result of the thermal phase change polymer stream k mergingwith the flow e.

FIG. 1 is a conceptual diagram for explaining an overview of anembodiment of the solvent separation system of the present invention.

The first step is a step for causing the feed stream a containing asolute and the solvent b to flow counter or parallel to the osmoticagent stream d through the semipermeable membrane o and cause thesolvent b contained in the feed stream a to pass through thesemipermeable membrane o and migrate into the osmotic agent stream d toobtain the flow e. In this first step, a unit A is used that has beendesigned so that the two flows can flow counter or parallel to eachother through the semipermeable membrane o.

In the first step, the feed stream a flows through the semipermeablemembrane o counter or parallel to the osmotic agent stream d in the unitA. As a result, the solvent b in the feed stream a migrates to theosmotic agent stream d through the semipermeable membrane o. Thismigration of the solvent b uses the semipermeable membrane o as aforward osmosis membrane and is the result of a forward osmosis process,and is preferable from the viewpoint of enabling solvent to be separatedefficiently while consuming only a small amount of energy.

The osmotic agent stream d becomes the flow e as a result the solventmigrating thereto and being mixed therein, and is then discharged fromthe unit A.

The second step is a step for mixing the flow e containing the solvent band the osmotic agent stream d with the thermal phase change polymerstream k at a mixing point α to obtain the flow f, followed byseparating the flow f containing the solvent b, the osmotic agent streamd and the thermal phase change polymer stream k into the osmotic agentstream d and the flow h containing the solvent b and the thermal phasechange polymer stream k.

In a certain embodiment of the present invention, a cooling device q1and a separator A are used in this second step.

In the flow f, migration of the solvent b from the flow e into thethermal phase change polymer stream k occurs due to mixing of the flow eand the thermal phase change polymer stream k. The use of the coolingdevice q1 at an intermediate location of this flow f makes it possibleto promote migration of the solvent b into the thermal phase changepolymer stream k. A chiller or heat exchanger, for example, can be usedfor the cooling device q1.

Any separator may be used for the separator A provided it has a functionthat separates the flow f into the thermal phase change polymer stream kcontaining the solvent b (namely, flow h) and the flow e from which thesolvent b is released (namely, osmotic agent stream d). For example, theseparator A can be a device having a suitable means for carrying outsuch separation such as a centrifugal separation device, gravitationalsedimentation device, coalescer or hydrocyclone.

In this second step, the relationship between the temperature Tk and thetemperature Tf is such that Tk−Tf=0.1° C. to 80° C., and the temperatureTf of the flow f after mixing is equal to higher than the cloud point ofthe flow f. More preferably, the relationship between the temperature Teand the temperature Tf is such that Te−Tf=0.1° C. to 80° C. Thetemperature Tk is the temperature of the aforementioned thermal phasechange polymer stream k at a location immediately before the mixingpoint α where the thermal phase change polymer stream k and flow econverge. The temperature Tf is the temperature of the aforementionedflow f at a location immediately before where the flow f enters theseparator A. The temperature Te is the temperature of the flow e at alocation immediately before the mixing point α where the flow econverges with the thermal phase change polymer stream k.

The temperature Tf of the flow f is a temperature that is higher thanthe cloud point of the flow f. The cloud point of the flow f as referredto here is the temperature at which clouding begins to occur when theflow f is heated from a low temperature at which it is uniformlydissolved. Thus, at least the flow f that enters the separator A is amixed flow composed of two phases consisting of the flow e and thethermal phase change polymer stream k.

The temperature Tf is preferably as low as possible within a range thatdoes not go below the cloud point of the flow f in order to promotemigration of the solvent b from the flow e into the thermal phase changepolymer stream k. On the other hand, a larger temperature differencebetween Tk and Tf is more disadvantageous in terms of energyconsumption. Thus, it is necessary for Tk−Tf to be within the range of0.1° C. to 80° C. The value of Tk−Tf is preferably 0.1° C. to 50° C. andmore preferably 0.1° C. to 30° C. However, the requirement that Tf beequal to or higher than the cloud point of the flow f must always besatisfied.

As was described above, the temperature Tf is preferably as low aspossible within a range that does not go below the cloud point of theflow f in order to promote migration of the solvent b from the flow e tothe thermal phase change polymer stream k. On the other hand, a largertemperature difference between Te and Tf is more disadvantageous interms of energy consumption. Thus, Te−Tf is preferably 0.1° C. to 80° C.The value of Te−Tf is more preferably 0.1° C. to 50° C. and even morepreferably 0.1° C. to 30° C. However, the requirement that Tf be equalto or greater than the cloud point of the flow f must always besatisfied.

The Tk, Tf and Te in this embodiment are specifically measured at thelocations of the black circles indicated with arrows denoted as Tk, Tfand Te, respectively, in the second step of FIG. 1.

In another embodiment of the present invention, a counter flowextraction device S is used instead of the cooling device q1 and theseparator A in this second step. FIG. 2 shows a conceptual diagram forexplaining an overview of the solvent separation system of the presentinvention in the case of using the counter flow extraction device S.

The following provides an explanation of the counter flow extractiondevice S.

It is necessary to mix and then separate the flow e and the thermalphase change polymer stream k in order to allow the solvent b to migratefrom the flow e into the thermal phase change polymer stream k.

The counter flow extraction device S refers to a device that allows theflow e and the thermal phase change polymer stream k to make counterflow contact. As a result of making counter flow contact, mixing andseparation can be carried out efficiently and the solvent b can beallowed to efficiently migrate from the flow e into the thermal phasechange polymer stream k. The flow e and the thermal phase change polymerstream k are injected and allowed to respectively make counter flowcontact such that the flow composed of liquid having a comparativelyhigh specific gravity is injected from the upper portion of the counterflow extraction device S while the flow composed of liquid having acomparatively low specific gravity is injected from the lower portion.For example, in the case of using a concentrated inorganic salt solutionfor the osmotic agent stream d and a polymer solution for the thermalphase change polymer stream k, the osmotic agent stream d is preferablyinjected from the upper portion since this stream normally has a highspecific gravity, while the thermal phase change polymer stream k ispreferably injected from the lower portion.

Examples of the counter flow extraction device S include a packedcolumn, spray column, sieve tray and rotating disc column. A specificexample thereof is the device explained and exemplified in the 7thEdition of the Chemical Engineering Handbook (edited by the Society ofChemical Engineers, Japan and published by Maruzen Publishing Co., Ltd.,ISBN978-4-621-08388-8). The counter flow extraction device S preferablyhas a temperature control function.

The counter flow extraction device S in the present invention does notrequire standing or centrifugal separation in order to carry outseparation provided the required column height can be ensured.Consequently, it is particularly advantageous for extracting betweenliquids that are difficult to separate and also makes it possible forthe solvent separation system to save on space.

An overview of an example of a counter flow extraction device Spreferably used in the present invention is shown in FIG. 3.

The temperature relationships of each component in the second step inthe case of using the counter flow extraction device S are the same asthose in the previously described case. However, the temperature Tsinside the counter flow extraction device S is used instead of thetemperature Tf of the flow f. Namely, in the second step, therelationship between the temperature Tk of the thermal phase changepolymer stream k prior to mixing and the temperature Ts inside thecounter flow extraction device S is such that Tk−Ts=0.1° C. to 80° C.,and more preferably the relationship between the temperature Te of theflow e prior to mixing and the temperature Ts inside the counter flowextraction device S is such that Te−Ts=0.1° C. to 80° C. The value ofTk−Ts is preferably 0.1° C. to 50° C. and more preferably 0.1° C. to 30°C. The value of Te−Ts is more preferably 0.1° C. to 50° C. and even morepreferably 0.1° C. to 30° C. The temperature Ts inside the counter flowextraction device S is always required to satisfy the requirement thatthe temperature Ts be equal to or higher than the cloud point of theliquid resulting from mixing the flow e and the thermal phase changepolymer stream k at a 1:1 ratio.

In this embodiment, Tk, Ts and Te are specifically measured at thelocations of the black circles indicated with arrows denoted as Tk, Tsand Te, respectively, in the second step of FIG. 2.

The third step of the solvent separation system of the present inventionis a step for heating the flow h followed by separating into the solventb and the thermal phase change polymer stream k. This third step is thesame for both the system shown in FIG. 1 and the system shown in FIG. 2.

This third step can be carried out using, for example, a heat exchangerq2 and a separator B.

The heat exchanger q2 is a heat exchanger that is used as necessary, andis a device that allows heat to be transferred from the thermal phasechange polymer stream k at a higher temperature to the flow h at a lowertemperature.

The separator B refers to a device that allows the solvent b to migratefrom the flow h, and is operated at a temperature equal to or higherthan the cloud point of the flow h. The cloud point of the flow h refersto the temperature at which clouding begins to occur when the flow h isheated to a higher temperature from a low temperature at which it isuniformly dissolved. Thus, the flow h is separated into the solvent band a thermal phase change polymer-rich phase in the aforementionedseparator B. At this time, the operational temperature of the separatorB is preferably set so that the concentration of the thermal phasechange polymer in the polymer-rich phase following separation is equalto the concentration of the thermal phase change polymer of the thermalphase change polymer stream k.

Examples of the separator B include a device having one or more types ofmeans selected from a centrifugal separation device, gravitationalsedimentation device, coalescer, hydrocyclone and filtering unit (suchas that carrying out solid-liquid separation or oil-water separation).

There are cases in which the solvent b separated by the separator Bcontains trace amounts of impurities. Thus, depending on the case, anadditional purification means can be added for the solvent b dischargedfrom the separator B. Examples of additional purification means includenanofiltration, reverse osmosis filtration, ultrafiltration,microfiltration, ion exchange resin, activated charcoal and varioustypes of adsorbent materials. Concentrated liquid obtained bynanofiltration or other form of membrane filtration from thispurification means may be returned to the first step, second step orthird step, or may be discarded.

Although the cloud point of the flow h is preferably sufficiently highin comparison with room temperature, an excessively high cloud point isdisadvantageous in terms of energy consumption. Thus, the cloud point ofthe thermal phase change polymer stream h is preferably 40° C. to 200°C., more preferably 50° C. to 180° C., and even more preferably 50° C.to 150° C.

The following provides an explanation of another embodiment of thesystem of the present invention with reference to additional drawings.

Examples of systems of other embodiments of the present invention areshown in FIGS. 4 and 5.

The system shown in FIG. 4 is the same as the system shown in theaforementioned FIG. 1 with the exception of using a compound unitcomposed of a flocculation tank and a filtering unit having asemi-permeable membrane p.

This flocculation tank has a function that separates the flow h into athermal phase change polymer-rich stream j and a solvent-rich stream 1using the principle of gravitational sedimentation or centrifugalseparation. The solvent-rich stream 1 is introduced into a purificationunit. The solvent b in the solvent-rich stream 1 is purified by thispurification unit.

The purification unit shown in FIG. 4 is equipped with a semi-permeablemembrane p that has a function that allows permeation of solvent butdoes not allow permeation of solute. Solvent purification carried out bythe purification unit can be carried out by, for example, a reverseosmosis membrane method, microfiltration method, ultrafiltration method,nanofiltration method, pervaporation method, perdistillation method ormembrane distillation, and these methods can be used alone or incombination.

A flow m, in which the thermal phase change polymer has beenconcentrated following migration and removal of solvent, is reused withthe stream j as the thermal phase change polymer stream k.

As a result of configuring the separator B in the third step in the formof a compound unit in this manner, the purity of the ultimately obtainedpurified solvent can be further improved.

The system shown in FIG. 5 is the same as the system shown in theaforementioned FIG. 4 with the exception of respectively installing amixer for mixing the flow e with the thermal phase change polymer streamk in the second step and a stirrer used prior to separation of the flowh in the third step.

The installation of the aforementioned mixer in the second step promotesmixing of the flow e and the stream k.

The installation of the aforementioned stirrer in the third step offersthe advantage of allowing the third step to proceed smoothly when theflow h is separated into two phases consisting of the thermal phasechange polymer-rich stream j and the solvent-rich stream 1.

In the systems shown in FIGS. 4 and 5, an aspect using a counter flowextraction device for the separation means of the second step can alsobe preferably employed as a specific embodiment of the presentinvention.

Reference symbols p1, p2 and p3 shown in FIGS. 1 to 5 referred to duringthe aforementioned explanations are each pumps for feeding liquids.

As has been previously described, the solvent b can be recovered fromthe feed stream a at high purity as a result of going through the firststep, second step and third step of the present invention.

EXAMPLES

The following provides an explanation of the present invention based onexamples thereof.

Number-average molecular weight as referred to in the following examplesand comparative examples is the number-average molecular weight based onpolystyrene as measured by gel permeation chromatography (GPC) using thedevice indicated below.

Device: Tosoh Corp., HLC-8220GPC

Columns: Tosoh Corp., TSKgel G1000HXL×1 column, TSKgel G2000HXL×1 columnand TSKgel G3000HXL×1 column

Carrier: Wako Pure Chemical Industries, Ltd., special gradetetrahydrofuran

Detection method: Differential refractometer

Carrier flow rate: 1.0 mL/min

Calibration curve: Tosoh Corp., TSK standard polystyrenes

Column chamber internal temperature: 40° C.

Sample concentration: 0.05% by weight to 0.1% by weight

Sample injection volume: 50 μL

A thermocouple (k type) was installed at the corresponding location foreach temperature and the temperature displayed by the LT370 manufacturedby Chino Corp. connected to the thermocouple was read therefrom.

The primary effect of the present invention is to increase the amount ofsolvent that migrates from the flow e to the flow h by controllingtemperature in the second step. Thus, the following Examples 1 to 16 andComparative Examples 1 to 4 were investigated while focusing on themigration of solvent (water) in the second step.

Examples 1 to 4 and Comparative Example 1

Examples 1 to 4 and Comparative Example 1 were carried out using thesystem shown in FIG. 1.

Water was used for the solvent b, ammonium sulfate was used for theosmosis agent, and Epan® 450 (copolymer of polyethylene oxide andpolypropylene oxide, number-average molecular weight: 2,400, DKS Co.,Ltd.) was used for the thermal phase change polymer. The concentrationof ammonium sulfate in the osmotic agent stream d was 10% by weight andthe concentration of Epan 450 in the thermal phase change polymer streamk was 75% by weight.

A forward osmosis unit was used for the unit A in the first step, acentrifugal separation unit was used for the separator A in the secondstep, and a purification unit composed of a flocculation tank forgravitational sedimentation and reverse osmosis membrane was used forthe separator B in the third step. Seawater was used for the feed streama and the feed rate thereof was 120 L/min. The flow rate of the osmoticagent stream d was 120 L/min and the flow rate of the thermal phasechange polymer stream k was 120 L/min.

The composition of the flow e, the composition of the thermal phasechange polymer stream k, and the composition of the flow h followingseparation with the separator A when the temperature Te of the flow e,the temperature Tk of the thermal phase change polymer stream k and thetemperature Tf of the flow f were respectively adjusted as shown inTable 1 were investigated and the amount of water migrating from theflow e to the flow h (difference between the amount of water in the flowh and the amount of water in the thermal phase change polymer stream k)was confirmed. Te, Tk and Tf were measured at the locations of the blackcircles specified by the arrows denoted with Te, Tk and Tf,respectively, in the second step shown in FIG. 1.

The composition of the flow e in Examples 1 to 4 and Comparative Example1 consisted of 28.0 g of water and 2.0 g of ammonium sulfate based on atotal amount of 30.0 g. Other values are shown in Table 1.

TABLE 1 Comp. Example 1 Example 2 Example 3 Example 4 Ex. 1 TemperatureTe 25° C. 25° C. 25° C. 25° C. 25° C. Tk 30° C. 30° C. 30° C. 40° C. 25°C. Tf  5° C. 10° C. 20° C.  7° C. 40° C. Te − Tf 20° C. 15° C.  5° C.18° C. −15° C.  Tk − Tf 25° C. 20° C. 10° C. 33° C. −15° C.  Cloud pointFlow f <0° C. <0° C. <0° C. <0° C. <0° C. Flow k 90° C. 90° C. 90° C.90° C. 90° C. Flow h 71° C. 73° C. 75° C. 72° C. 81° C. Composition Flowk h k h k h k h k h Total 30.0 49.2 30.0 47.6 30.0 46.1 30.0 48.4 30.040.0 amount. (g) Water (g) 7.5 26.7 7.5 25.1 7.5 23.6 7.5 25.9 7.5 17.5Polymer (g) 22.5 22.5 22.5 22.5 22.5 22.5 22.5 22.5 22.5 22.5 Watermigration 19.2 17.6 16.1 18.4 10 from e to h (g)

Examples 5 to 8 and Comparative Example 2

Examples 5 to 8 and Comparative Example 2 were carried out using thesame method as Examples 1 to 4 and Comparative Example 1 with theexception of using sodium thiosulfate and sodium sulfite as osmoticagents and making the concentration of sodium thiosulfate to be 10% byweight and the concentration of sodium sulfite to be 0.5% by weight inthe osmotic agent stream d, and the amount of water migrating from theflow e to the flow h was confirmed when adjusting the temperature Te ofthe flow e, temperature Tk of the thermal phase change polymer stream kand temperature Tf of the flow f as described in Table 2.

The composition of the flow e in Examples 5 to 8 and Comparative Example2 consisted of 28.0 g of water and a total of 2.0 g of sodiumthiosulfate and sodium sulfite based on a total amount of 30.0 g. Othervalues are shown in Table 2.

TABLE 2 Comp. Example 5 Example 6 Example 7 Example 8 Ex. 2 TemperatureTe 25° C. 25° C. 25° C. 25° C. 25° C. Tk 30° C. 30° C. 30° C. 40° C. 25°C. Mixer 28° C. 28° C. 28° C. 33° C. 25° C. Tf  5° C. 10° C. 20° C.  7°C. 40° C. Te − Tf 20° C. 15° C.  5° C 18° C. −15° C.  Tk − Tf 25° C. 20°C. 10° C. 33° C. −15° C.  Cloud point Flow f <0° C. <0° C. <0° C. <0° C.<0° C. Flow k 90° C. 90° C. 90° C. 90° C. 90° C. Flow h 70° C. 71° C.73° C. 70° C. 80° C. Composition Flow k h k h k h k h k h Total 30.050.1 30.0 49.2 30.0 47.8 30.0 49.8 30.0 41.4 amount. (g) Water (g) 7.527.6 7.5 26.7 7.5 25.3 7.5 27.3 7.5 18.9 Polymer (g) 22.5 22.5 22.5 22.522.5 22.5 22.5 22.5 22.5 22.5 Water migration 20.1 19.2 17.8 19.8 11.4from e to h (g)

Examples 9 to 12 and Comparative Example 3

Examples 9 to 12 and Comparative Example 3 were carried out using thesystem shown in FIG. 2.

Water was used for the solvent b, ammonium sulfate was used for theosmotic agent, and Pepol® AH-0673A (copolymer of ethylene oxide andpropylene oxide in which the hydroxyl group on one end is substitutedwith an allyl group, number-average molecular weight: 2,000, TohoChemical Industry Co., Ltd.) was used for the thermal phase changepolymer. The concentration of ammonium sulfate in the osmotic agentstream d was 30% by weight and the concentration of Pepol AH-0673A inthe thermal phase change polymer stream k was 80% by weight.

A forward osmosis unit was used for unit A in the first step, acylindrical packed column made of polyvinyl chloride, having a towerdiameter of 5 cm and a packing tower height of 3.5 m, and using apacking material having an outer diameter of 10 mm, inner diameter of 8mm and length of 10 mm for the packing material, was used for thecounter flow extraction device in the second step. A purification unitcomposed of a flocculation tank for gravitational sedimentation and areverse osmosis membrane was used for the separator B of the third step.Seawater was used for the feed stream a and the feed rate was 20 mL/min.The flow rate of the osmotic agent stream d was 20 mL/min and the flowrate of the thermal phase change polymer stream k was 20 mL/min.

The composition of the flow e, the composition of the thermal phasechange polymer stream k, and the composition of the flow h followingseparation with the counter flow extraction device when the temperatureTe of the flow e, temperature Tk of the thermal phase change polymerstream k and the temperature Ts within the counter flow extractiondevice S were respectively adjusted as shown in Table 3 wereinvestigated, and the amount of water migrating from the flow e to theflow h (difference between the amount of water in the flow h and theamount of water in the thermal phase change polymer stream k) wasconfirmed. Te, Tk and Ts were measured at the locations of the blackcircles specified by the arrows denoted with Te, Tk and Ts,respectively, in the second step shown in FIG. 2.

The composition of the flow e in Examples 9 to 12 and ComparativeExample 3 consisted of 22.8 g of water and 7.2 g of ammonium sulfatebased on a total amount of 30.0 g. Other values are shown in Table 3.

TABLE 3 Comp. Example 9 Example 10 Example 11 Example 12 Ex. 3Temperature Te 25° C. 25° C. 25° C. 40° C. 25° C. Tk 30° C. 30° C. 30°C. 40° C. 25° C. Ts 20° C. 15° C. 22° C. 37° C. 30° C. Te − Ts  5° C.10° C.  3° C.  3° C. −10° C.  Tk − Ts 10° C. 15° C.  8° C.  3° C. −10°C.  Cloud point Flow f <0° C. <0° C. <0° C. <0° C. <0° C. Flow k 135°C.  135° C.  135° C.  135° C.  135° C.  Flow h 98° C. 98° C. 99° C. 100°C.  111° C.  Composition Flow k h k h k h k h k h Total 30.0 34.5 30.034.7 30.0 34.2 30.0 33.5 30.0 31.3 amount. (g) Water (g) 6.0 10.5 6.010.7 6.0 10.2 6.0 9.5 6.0 7.3 Polymer (g) 24.0 24.0 24.0 24.0 24.0 24.024.0 24.0 24.0 24.0 Water migration 4.5 4.7 4.2 3.5 1.3 from e to h (g)

Examples 13 to 16 and Comparative Example 4

Examples 13 to 16 and Comparative Example 4 were carried out using thesame method as Examples 9 to 12 and Comparative Example 3 with theexception of using sodium thiosulfate and sodium sulfite as osmoticagents and using Uniox® AA-800 (polyethylene oxide having both endhydroxyl groups substituted with allyl groups, number-average molecularweight: 800, NOF Corp.) for the thermal phase change polymer, and makingthe concentration of the sodium thiosulfate 38% by weight and theconcentration of sodium sulfite 0.5% by weight in the osmotic agentstream d, and making the concentration of Uniox AA-800 70% by weigh inthe thermal phase change polymer stream k, and the amount of watermigrating from the flow e to the flow h was confirmed when thetemperature Te of the flow e, temperature Tk of the thermal phase changepolymer stream k and the temperature Ts within the counter flowextraction device S were respectively adjusted as shown in Table 4.

The composition of the flow e in Examples 13 to 16 and ComparativeExample 4 consisted of 22.8 g of water and 7.2 g of ammonium sulfatebased on a total amount of 30.0 g. Other values are shown in Table 4.

TABLE 4 Comp. Example 13 Example 14 Example 15 Example 16 Ex. 4Temperature Te 25° C. 25° C. 25° C. 40° C. 25° C. Tk 30° C. 30° C. 30°C. 40° C. 25° C. Ts 20° C. 15° C. 22° C. 37° C. 30° C. Te − Ts  5° C.10° C.  3° C.  3° C. −10° C.  Tk − Ts 10° C. 15° C.  8° C.  3° C. −10°C.  Cloud point Flow f <0° C. <0° C. <0° C. <0° C. <0 ° C.  Flow k 145°C.  145° C.  145° C.  145° C.  145° C.  Flow h 109° C.  108° C.  110°C.  111° C.  117° C.  Composition Flow k h k h k h k h k h Total 30.035.2 30.0 35.3 30.0 35.0 30.0 34.3 30.0 31.8 amount. (g) Water (g) 9.014.2 9.0 14.3 9.0 14.0 9.0 13.3 9.0 10.8 Polymer (g) 21.0 21.0 21.0 21.021.0 21.0 21.0 21.0 21.0 21.0 Water migration 5.2 5.3 5 4.3 1.8 from eto h (g)

According to the aforementioned embodiments, setting the temperature Tfof the flow f or the temperature Ts within the counter flow extractiondevice S to be lower than the temperature Tk of the thermal phase changepolymer stream k and the temperature Te of the flow e was shown to beadvantageous in terms of the amount of migrated water.

However, cooling energy, heating energy and motive power energy arerequired to actually operate the system of the present invention. Aninvestigation was therefore made in the following examples of therelationship between the total amount of energy consumed by the systemand the amount of purified water.

Examples 17 and 18

The following indicates the results obtained by simulating the totalamount of energy consumed by the system per unit amount of purifiedwater when water was purified using the system of the present invention.

Table 5 indicates the results of Example 17 that was carried out usingthe system of FIG. 1, while Table 6 indicates the results of Example 18that was carried out using the system of FIG. 2.

TABLE 5 Example 17 (System of FIG. 1) Tk (° C.) 41.0 39.0 37.4 35.0 32.0Tf (° C.) 41.0 38.0 35.0 30.0 22.0 Tk − Tf (° C.) 0.0 1.0 2.4 5.0 10.0Total amount of 0.37 0.32 0.31 0.33 0.37 energy consume per 1 t ofpurified water (kWh/t)

TABLE 6 Example 18 (System of FIG. 2) Tk (° C.) 42.0 39.0 36.5 34.0 30.0Ts (° C.) 42.0 38.0 33.0 29.0 20.6 Tk − Ts (° C.) 0.0 1.0 3.5 5.0 9.4Total amount of 0.35 0.30 0.27 0.28 0.36 energy consume per 1 t ofpurified water (kWh/t)

INDUSTRIAL APPLICABILITY

The system and method of the present invention can be preferably used infields targeted at the recovery of solvent from inorganic and organicsolutions. More specifically, the system and method of the presentinvention can be preferably used in fields such as the desalination ofseawater, regeneration of domestic wastewater, regeneration ofindustrial wastewater or recovery of produced water dischargedaccompanying excavation of oil fields and gas fields.

1. A solvent separation system, comprising: a first step for causing afeed stream a containing a solute and a solvent b to flow counter orparallel to an osmotic agent stream d through a semipermeable membrane oand causing the solvent b contained in the feed stream a to pass throughthe semipermeable membrane o and migrate into the osmotic agent stream dto obtain a flow e, a second step for mixing the flow e containing thesolvent b and the osmotic agent stream d with a thermal phase changepolymer stream k to obtain a flow f, followed by separating the flow fcontaining the solvent b, the osmotic agent stream d and the thermalphase change polymer stream k into the osmotic agent stream d and a flowh containing the solvent b and the thermal phase change polymer streamk, and a third step for heating the flow h followed by separating intothe solvent b and the thermal phase change polymer stream k; wherein,the second step simultaneously satisfies the following conditions (1)and (2): (1) the relationship between a temperature Tk of the thermalphase change polymer stream k prior to mixing and a temperature Tf ofthe flow f after mixing is such that Tk−Tf=0.1° C. to 80° C., and (2)the temperature Tf of the flow f after mixing is equal to or higher thanthe cloud point of the flow f.
 2. The system according to claim 1,wherein the relationship between a temperature Te of the flow e prior tomixing and the temperature Tf of the flow f after mixing is such thatTe−Tf=0.1° C. to 80° C.
 3. The system according to claim 1, wherein thesolvent b is water.
 4. The system according to claim 1, wherein thethermal phase change polymer contained in the thermal phase changepolymer stream k is a copolymer of ethylene oxide and propylene oxide,and the ends thereof are either hydroxyl groups or one or more of theend hydroxyl groups is substituted with one or more types of groupsselected from the group consisting of an alkyl group, phenyl group,allyl group and aryl group.
 5. The system according to claim 1, whereinthe flow h containing the solvent b and the thermal phase change polymerstream k has a cloud point between 50° C. to 200° C.
 6. The systemaccording to claim 1, wherein the osmotic agent contained in the osmoticagent stream d is one or more types selected from the group consistingof an inorganic base, organic base, salt, ionic polymer, ionic liquid,nonionic polymer and organic compound.
 7. The system according to claim1, wherein the first step is carried out by a forward osmosis process.8. A solvent separation method, comprising: separating a solvent b froma feed stream a containing the solvent b and a solute selected from aninorganic compound and an organic compound using the system according toclaim
 1. 9. A solvent separation system, comprising: a first step forcausing a feed stream a containing a solute and a solvent b to flowcounter or parallel to an osmotic agent stream d through a semipermeablemembrane o and causing the solvent b contained in the feed stream a topass through the semipermeable membrane o and migrate into the osmoticagent stream d to obtain a flow e, a second step for introducing theflow e, containing the solvent b and the osmotic agent stream d, and athermal phase change polymer stream k into a counter flow extractiondevice S to cause the solvent b to migrate from the flow e into thethermal phase change polymer stream k followed by separating into theosmotic agent stream d and a flow h containing the solvent b and thethermal phase change polymer stream k, and a third step for heating theflow h followed by separating into the solvent b and the thermal phasechange polymer stream k.
 10. The system according to claim 9, whereinthe relationship between a temperature Tk of the thermal phase changepolymer stream k prior to mixing and a temperature Ts within the counterflow extraction device S in the second step is such that Tk−Ts=0.1° C.to 80° C.
 11. The system according to claim 9, wherein the relationshipbetween a temperature Te of the flow e prior to mixing and thetemperature Ts within the counter flow extraction device S in the secondstep is such that Te−Ts=0.1° C. to 80° C.
 12. The system according toclaim 9, wherein the solvent b is water.
 13. The system according toclaim 9, wherein the thermal phase change polymer contained in thethermal phase change polymer stream k is a copolymer of ethylene oxideand propylene oxide, and the ends thereof are either hydroxyl groups orone or more of the end hydroxyl groups is substituted with one or moretypes of groups selected from the group consisting of an alkyl group,phenyl group, allyl group and aryl group.
 14. The system according toclaim 9, wherein the flow h containing the solvent b and the thermalphase change polymer stream k has a cloud point between 50° C. to 200°C.
 15. The system according to claim 9, wherein the osmotic agentcontained in the osmotic agent stream d is one or more types selectedfrom the group consisting of an inorganic base, organic base, salt,ionic polymer, ionic liquid, nonionic polymer and organic compound. 16.The system according to claim 9, wherein the first step is carried outby a forward osmosis process.
 17. A solvent separation method,comprising: separating a solvent b from a feed stream a containing thesolvent b and a solute selected from an inorganic compound and anorganic compound using the system according to claim
 9. 18. A solventseparation device, provided with: a unit A that has a structure in whicha feed stream a and an osmotic agent stream d flow through asemipermeable membrane o in the form of counter flow or parallel flow,and has an inlet port for the feed stream a, a discharge port for a flowc obtained after the feed stream a has flown counter or parallel to theosmotic agent stream d through the semipermeable membrane o, an inletport for the osmotic agent stream d, and a discharge port for a flow eobtained after the osmotic agent stream d has flown counter or parallelto the feed stream a through the semipermeable membrane o, a counterflow extraction device S that has a structure in which the flow e iscaused to flow counter to the thermal phase change polymer stream k andthe solvent b in the flow e is extracted into the thermal phase changepolymer stream k to obtain a flow h, and has an inlet port for the flowe and a discharge port for the flow e following extraction, an inletport for the thermal phase change polymer stream k, a discharge port forthe flow h, and a temperature control function, and a unit B that has aheat exchanger q2 for heating the flow h and a separator B, wherein theseparator B has a function that separates the flow h into the thermalphase change polymer stream k and the solvent b, and the separator B hasan inlet port for the flow h, a discharge port for the thermal phasechange polymer stream k, and a discharge port for the solvent b.